The present invention relates to a resin composition comprising a saponified ethylene-vinyl acetate copolymer (hereinafter referred to briefly as EVOH) and a laminate comprising the same. More particularly, the invention relates to a resin composition capable of providing shaped articles outstanding in such characteristics as gas barrier properties, low-temperature heat drawability, long-run melt moldability, and appearance and to a laminate comprising said resin composition, such as a multi-lamellar vessel.
EVOH generally is good in clarity, gas barrier properties, aroma retentivity, solvent resistance and oil resistance, among other properties, and, exploiting these features, have heretofore been used in various packaging applications, namely as packaging materials for foods, pharmaceuticals, industrial chemicals and agrochemicals.
The sheet (inclusive of film) of EVOH is frequently stretched under heating for improving its mechanical strength and other properties and the heat-drawability of an exclusive EVOH sheet or a multi-layer sheet comprising an EVOH layer is an important requirement.
Particularly in recent years, a multi-lamellar vessel comprising a laminate comprised of a polystyrene resin layer and an EVOH layer, which is excellent in rigidity, clarity and surface gloss, is attracting attention. Thus, a multi-lamellar vessel having a laminar structure having a polystyrene resin layer on either side, i.e. the inside and outside of the vessel, namely xe2x80x9cthe polystyrene resin layer/adhesive resin layer/EVOH layer/adhesive resin layer/polystyrene layerxe2x80x9d and a multi-lamellar vessel comprising a polyethylene layer, which has good heat sealability by itself, as the innermost layer constituting the inside wall of the vessel and a polystyrene resin layer as the outermost layer constituting the outside wall of the vessel, namely the xe2x80x9cpolyethylene resin layer/adhesive resin layer/EVOH layer/adhesive resin layer/polystyrene resin layerxe2x80x9d are demanded by the market as very useful packaging materials.
Furthermore, laminates not using polystyrene resin, such as one having the xe2x80x9cpolyethylene resin layer/adhesive resin layer/EVOH layer/adhesive resin layer/polyethylene resin layer structurexe2x80x9d and one having the xe2x80x9cpolyethylene resin layer/adhesive resin layer/EVOH layer/adhesive resin layer/polypropylene resin layer structurexe2x80x9d are also demanded by the ecology-conscious market.
However, EVOH is inferior to thermoplastic resins such as polystyrene and polyolefin in heat-drawability or heat-moldability. To overcome this drawback, the following corrective methods, among others, have so far been proposed.
(1) The method which comprises adding a plasticizer to EVOH (JP Kokai S53-88067; JP Kokai H59-20345).
(2) The method which comprises blending a polyamide resin with EVOH (JP Kokai S52-141785; JP Kokai S58-36412).
(3) The method which comprises using a resin composition comprising two or more different grades of EVOH (JP Kokai S61-4752, S60-173038, S63-196645, S63-230757, S63-264656, H2-261847).
(4) The method which comprises blending a copolymer polyamide resin having a defined melting point with EVOH (JP Kokai S62-225543, S62-225544, S63-114645).
However, detained investigations by the present inventors revealed that the EVOH compositions described in the above literature have the following disadvantages.
The compositions disclosed in the above first group (1) of literature are drastically handicapped in gas barrier properties.
The compositions disclosed in the second group (2) of literature tend to be low in long-run melt-moldability.
The compositions disclosed in the above third and fourth groups (3) and (4) of literature have been somewhat improved in heat-drawability but are not satisfactory enough for use in applications where laminates with a polystyrene resin are heat-drawn in a high draw ratio at a low temperature, and have room for further improvement.
In addition, there is room for improvement in the appearance of a multi-lamellar vessel and in deep-drawability.
Under the circumstances, the present invention has for its object to provide an EVOH resin composition capable of providing shaped articles outstanding in gas barrier properties, low-temperature heat-drawability, long-run melt-moldability and appearance, among other characteristics, and a multi-lamellar vessel or other laminate comprising said resin composition.
The resin composition of the invention comprises a saponified ethylene-vinyl acetate copolymer (A), a polyamide resin having a melting point of not higher than 160xc2x0 C. (B), and a boron compound (C).
The laminate of the invention is a multi-lamellar shaped article comprising a resin composition layer (X) composed of a saponified ethylene-vinyl acetate copolymer (A), a polyamide resin (B) having a melting point not exceeding 160xc2x0 C., and a boron compound (C) and, as disposed on at least one side of said layer (X), a thermoplastic resin layer (Y). A representative example of said laminate is a heat-drawn multi-lammelar vessel as draw-molded in a draw ratio of 4xcx9c20.
The invention is now described in detail.
 less than EVOH (A) greater than 
The EVOH (A) for use in the invention is not particularly restricted but is preferably one having an ethylene content of 10xcx9c70 mole % (especially 20xcx9c60 mole %, particularly 25xcx9c50 mole %) and a saponification degree of not less than 90 mole % (especially not less than 95 mole %, particularly not less than 99 mole %) If the ethylene content is less than 10 mole %, the high-temperature gas barrier properties, melt-moldability and appearance will become inadequate. On the other hand, if it exceeds 70 mole %, no sufficient gas barrier properties will be obtained. If the degree of saponification is less than 90 mole %, the gas barrier properties, thermal stability and moisture resistance will be inadequate.
The melt flow rate (MFR) (as measured at 210xc2x0 C. under a load of 2160 g) of EVOH (A) is not particularly restricted but is preferably in the range of 0.5xcx9c100 g/10 min (especially 1xcx9c50 g/10 min, particularly 3xcx9c35 g/10 min). If the melt flow rate is below the above-mentioned range, the extruder interior will develop a high-torque condition at molding to make extrusion difficult. On the other hand, if the MFR is in excess of the above-mentioned range, the thickness accuracy of the shaped article tends to be decreased.
EVOH (A) can be obtained by saponifying an ethylene-vinyl acetate copolymer (EVA) produced by the known polymerization technology such as solution polymerization, suspension polymerization or emulsion polymerization. The saponification of the ethylene-vinyl acetate copolymer (EVA) can also be carried out by the known technology.
The EVOH (A) mentioned above may have been xe2x80x9ccopolymerization-modifiedxe2x80x9d with a copolymerizable ethylenically unsaturated monomer up to the extent not interfering with the effect of the invention. The monomer which can be used in this manner includes
olefins such as propylene, 1-butene, isobutene, etc.;
unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, phthalic acid (anhydride), maleic acid (anhydride), itaconic acid (anhydride), etc. and their salts or mono- or dialkyl (C1-18) esters;
acrylamides such as acrylamide, N-(C1-18)alkylacrylamides, N,N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid and its salts, and acrylamidopropyldimethylamine and its acid salts or quaternary salts;
methacrylamides such as methacrylamide, N-(C1-18)alkylmethacrylamides, N,N-dimethylmethacrylamide, 2-methacrylamidopropanesulfonic acid and its salts, methacrylamidopropyldimethylamine and its acid salts or quaternary salts;
N-vinylamides such as N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, etc.;
vinyl cyanides such as acrylonitrile, methacrylonitrile, etc.;
vinyl ethers such as (C1-18) alkyl vinyl ethers, hydroxyalkyl vinyl ethers, alkoxyalkyl vinyl ethers, etc.;
vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, vinyl bromide, etc.;
vinylsilanes such as trimethoxyvinylsilane etc.;
allyl acetate, allyl chloride, allyl alcohol, dimethylallyl alcohol,
trimethyl (3-acrylamido-3-dimethylpropyl)ammonium chloride,
acrylamido-2-methylpropanesulfonic acid and so on.
Furthermore, it may be a post-modified EVOH as obtained by urethanation, acetalization, cyano-ethylation or the like.
As the EVOH (A), two or more different grades of EVOH may be used. Thus, it is possible to use a blend of EVOH species varying in ethylene content by not less than 5 mole % or varying in the degree of saponification by not less than 1 mole %, or a blend of EVOH species with MFR ratios of not less than 4. To use a blend of EVOH species is useful, because it may contribute to improved flexibility, heat-moldability and film-making stability while the gas barrier properties are sustained.
 less than Polyamide Resin (B) greater than 
The polyamide resin (B) for use in the invention must have a melting point of not more than 160xc2x0 C. Use of a polyamide resin melting at a temperature higher than 160xc2x0 C. will not be rewarded with the effect of the invention. The melting-point range is preferably 80xcx9c150xc2x0 C., more preferably 80xcx9c140xc2x0 C.
The melting point in the present context represents the peak melting temperature (xc2x0 C.) as measured using a differential scanning calorimeter at a temperature-raising speed of 10xc2x0 C./min.
The polyamide resin (B) specifically includes:
polycarproamide (nylon 6),
poly-xcfx89-aminoheptanoic acid (nylon 7)
poly-xcfx89-aminononanic acid (nylon 9),
polyundecanamide (nylon 11),
polylaurolactam (nylon 12),
polyethylenediamineadipamide (nylon 26),
polytetramethyleneadipamide (nylon 46),
polyhexamethyleneadipamide (nylon 66),
polyhexamethylenesebacamide (nylon 610),
polyhexamethylenedodecamide (nylon 612),
polyoctamethyleneadipamide (nylon 8, 6),
polydecamethyleneadipamide (nylon 108),
caprolactam/laurolactam copolymer (nylon 6/12),
caprolactam/xcfx89-aminononanoic acid copolymer (nylon 6/9),
caprolactam/hexamethylenediammonium adipate copolymer (nylon 6/66),
laurolactam/hexamethylenediammonium adipate copolymer (nylon 12/66),
ethylenediamineadipamide/hexamethylenediammonium adipate copolymer (nylon 26/66),
caprolactam/hexamethylenediammonium adipate/hexamethylenediammonium sebacate copolymer (nylon 66/610),
ethyleneammonium adipate/hexamethylenediammonium adipate/hexamethylenediammonium sebacate copolymer (nylon 6/66/610),
polyhexamethyleneisophthalamide,
polyhexamethyleneterephthalamide,
hexamethyleneisophthalmide/terephthalamide copolymer, and so on.
Among such polyamide resins as modified with an aromatic amine such as methylenebenzylamine, m-xylenediamine or the like, those resins having melting points not higher than 160xc2x0 C. can also be used.
The method of adjusting the melting point of a polyamide resin to a temperature not exceeding 160xc2x0 C. is not particularly restricted. However, it is industrially preferable to use, among said polyamide resins, copolymer resins having certain comonomer ratios, such as nylon 6/12, nylon 6/69, nylon 6/66/610, nylon 6/66/610/12, nylon 6/66/610/11 etc. and the corresponding aromatic amine-modified copolymers. Specific commercial products include
xe2x80x9cAmilan CM4000xe2x80x9d, xe2x80x9cAmilan CM8000xe2x80x9d, xe2x80x9cAmilan CM6541xc3x973xe2x80x9d, xe2x80x9cAmilan CM831xe2x80x9d and xe2x80x9cAmilan CM833xe2x80x9d, all of which are products of Toray Co., Ltd.;
xe2x80x9cErvamide 8061xe2x80x9d, xe2x80x9cErvamide 8062Sxe2x80x9d and xe2x80x9cErvamide 8066xe2x80x9d, all of which are products of DuPont Japan;
xe2x80x9cGrilon CF6Sxe2x80x9d xe2x80x9cGrilon CF62BSxe2x80x9d, xe2x80x9cGrilon CA6Exe2x80x9d, xe2x80x9cGrilon XE3381xe2x80x9d and xe2x80x9cGrilon BM13SBGxe2x80x9d, all of which are products of EMS-Japan; and
xe2x80x9cUBE7128Bxe2x80x9d and xe2x80x9cUBE7028xe2x80x9d, both of which are products of Ube Industries, Ltd., among others.
The amount of heat of fusion xcex94H of the polyamide resin (B) as determined with a differential scanning calorimeter (temperature-raising speed 10xc2x0 C./min) is preferably not more than 80 J/g (more preferably 5xcx9c70 J/g, particularly 10xcx9c60 J/g). If the amount of heat of fusion xcex94H exceeds 80 J/g, the low-temperature heat-drawability tends to be decreased.
The melt flow rate (MFR) (210xc2x0 C., load 2160 g) of the polyamide resin (B) is preferably 1xcx9c100 g/10 min (more preferably 5xcx9c80 g/10 min, particularly 8xcx9c50 g/10 min. If the melt flow rate deviates from the above range, the low-temperature heat-drawability tends to be decreased.
In the present invention, two or more species of said polyamide resin (B) varying in structure, composition, molecular weight (relates to MFR) and molecular weight distribution may be optionally used in combination.
 less than Boron Compound (C) greater than 
The boron compound (C) which can be used in the invention includes boric acid, calcium borate, cobalt borate, zinc borate (zinc tetraborate, zinc metaborate, etc.), aluminum potassium borate, ammonium borate (ammonium metaborate, ammonium tetraborate, ammonium pentaborate, ammonium octaborate, etc.), cadmium borate (cadmium orthoborate, cadmium tetraborate, etc.), potassium borate (potassium metaborate, potassium tetraborate, potassium pentaborate, potassium hexaborate, potassium octaborate, etc.), silver borate (silver metaborate, silver tetraborate, etc.), copper borate (cupric borate, copper metaborate, copper tetraborate, etc.), sodium borate (sodium metaborate, sodium diborate, sodium tetraborate, sodium pentaborate, sodium hexaborate, sodium octaborate, etc.), lead borate (lead metaborate, lead hexaborate, etc.), nickel borate (nickel orthoborate, nickel diborate, nickel tetraborate, nickel octaborate, etc.), barium borate (barium orthoborate, barium metaborate, barium diborate, barium tetraborate, etc.), bismuth borate, magnesium borate (magnesium orthoborate, magnesium diborate, magnesium metaborate, trimagnesium tetraborate, pentamagnesium tetraborate, etc.), manganese borate (manganese borate, manganese metaborate, manganese tetraborate, etc.), and lithium borate (lithium metaborate, lithium tetraborate, lithium pentaborate, etc.), among others. Furthermore, borate minerals such as borax, cahnite, inyoite, kotoite, suanite, azaibelyite, etc. can also be mentioned.
The preferred, among these, are borax, boric acid and sodium borate (sodium metaborate, sodium diborate, sodium tetraborate, sodium pentaborate, sodium hexaborate, sodium octaborate, etc.).
The mechanism of action of the invention is not definitely clear but it is suspected that the boron compound (C) acts on the functional group (OH) of EVOH (A) and the functional group (amide group) of polyamide resin (B) to suppress the thermal degradation associated with interaction of the two resins (A) and (B) and, at the same time, contribute somewhat to their interaction with the thermoplastic resin in the adjoining layer, with the result that both long-run melt-moldability and low-temperature heat-drawability are improved. It is apparent from the comparison of examples of the invention with comparative examples which is made hereinafter that the boron compound (C) contributes to both long-run melt-moldability and heat-drawability.
 less than Formulating Ratio of (A), (B) and (C) Components greater than 
The formulating ratio of components (A), (B) and (C) in the composition is not particularly restricted but the A/B ratio of EVOH (A) to polyamide resin (B) is preferably 50/50xcx9c99/1 (more preferably 60/40xcx9c97/3, particularly 70/30xcx9c95/5) by weight. If this weight ratio is smaller than 50/50, the gas barrier properties will be insufficient. On the other hand, if the ratio exceeds 99/1, the low-temperature heat-drawability and appearance tend to be inadequate.
Based on 100 weight parts of the EVOH (A) and polyamide resin (B) combined, the boron compound (C) is preferably formulated in a proportion of 0.001xcx9c1 weight part (more preferably 0.002xcx9c0.5 wt. part, particularly 0.005xcx9c0.2 wt. part) as B. If the proportion is less than 0.001 weight part, the long-run melt-moldability and heat-drawability will be insufficient. On the other hand, if the proportion exceeds 1 weight part, the appearance of the shaped article will be adversely affected.
 less than Formulating Procedure greater than 
The resin composition comprising the above-described components (A), (B) and (C) according to the invention can be simply obtained by blending said components (A), (B) and (C), specifically by any of the following methods.
(1) The components (A), (B) and (C) are blended all at once and, then, melt-kneaded.
(2) The component (A) is blended with the component (B), the component (C) is then added, and the whole mixture is melt-kneaded.
(3) The component (C) is incorporated in the component (A), then the component (B) is added, and the whole mixture is melt-kneaded.
(4) The component (C) is incorporated in the component (B), then the component (A) is added, and the whole mixture is melt-kneaded.
(5) The component (C) is incorporated in both the components (A) and (B), which are then melt-kneaded together.
(6) Each of the components (A), (B) and (C) is dissolved homogeneously in a solvent, the solutions are mixed, and the solvent is removed.
Among these methods, the method (3) is preferred and, therefore, will be described in further detail.
The boron compound (C) can be incorporated in EVOH (A) by contacting the EVOH (A) with an aqueous solution of the boron compound (C). The concentration of boron compound (C) in the aqueous solution is preferably 0.001xcx9c1 weight % (more preferably 0.005xcx9c0.8 weight %, particularly 0.01xcx9c0.5 weight %) as B. If it is less than 0.001 weight %, the necessary amount of boron compound (C) may not be easily incorporated. On the other hand, if it exceeds 1 weight %, the appearance of the shaped article as the end product tends to be inadequate.
The method of contacting EVOH (A) with said aqueous solution of boron compound (C) is not particularly restricted but the method which comprises adding pellets of EVOH (A) to the aqueous solution and stirring the mixture can be generally employed and, in this manner, the boron compound (C) can be successfully incorporated in the pellets of EVOH (A).
Referring to the preparation (molding) of said EVOH (A) pellets, the known technology can be utilized. A typical procedure comprises extruding a solution of EVOH (A) in water-alcohol in the form of a strand or sheet in a coagulation bath and cutting the coagulated strand or sheet into pellets. The preferred shape of the EVOH (A) pellet is a cylinder or a sphere. The cylinder is preferably 1xcx9c10 mm in diameter and 1xcx9c10 mm long, and the sphere is preferably 1xcx9c10 mm in diameter.
In order that the boron compound (C) may be uniformly incorporated, the EVOH (A) obtained by the above coagulation procedure preferably has a microporous internal structure with a multiplicity of pores as fine as about 0.1xcx9c10 xcexcm in diameter uniformly distributed and an EVOH (A) having such an internal structure can be generally obtained by controlling the conditions of extrusion of the EVOH solution (e.g. in water-alcohol) in a coagulation bath, such as the concentration of said EVOH solution (20xcx9c80 weight %) extrusion temperature (45xcx9c70xc2x0 C.), type of solvent (water/alcohol=80/20xcx9c5/95, by weight), coagulation bath temperature (1xcx9c20xc2x0 C.), residence time (0.25xcx9c30 hours) and the level of EVOH in the coagulation bath (0.02xcx9c2 weight %), among other parameters.
Moreover, the water content of said pellets of EVOH (A) is preferably 20xcx9c80 weight %, for the boron compound (C) can then be uniformly and rapidly incorporated.
The method of adjusting the level of boroncompound (C) relative to EVOH (A) is not particularly restricted. However, this can be achieved by controlling the conditions of contact of EVOH (A) with the aqueous solution of boron compound (C), such as the concentration of the aqueous solution of boron compound (C), duration of contact, contact temperature, rate of agitation in contacting, and the water content of the EVOH (A) to be treated, among other parameters.
The hydrous EVOH (A) pellets containing the boron compound (C) can thus be obtained and the pellets so obtained are generally dried.
This drying can be effected by various methods. For example, the fluidized drying method in which a drying load in pellet form is agitated and dispersed substantially by a mechanical means or by means of a hot air current and the stationary drying method in which pellets are dehydrated substantially without being subjected to a dynamic action such as stirring or dispersing can be mentioned. The dryer which can be used for fluidized drying includes the cylinder-channel type stirring dryer, cylindrical dryer, rotary dryer, fluidized-bed dryer, vibratory fluidized-bed dryer and conical rotary dryer, among others. As regards the dryer which can be used for stationary drying, there can be mentioned the box-type batch dryer which is of the load-stationary type and the band dryer, tunnel dryer, vertical dryer and the like, all of which are of the load-moving type. It should be understood that these dryers are not exclusive choices. Moreover, fluidized drying and stationary drying can be carried out in combination.
The warm or hot gas to be used for said drying includes air and inert gases (nitrogen gas, helium gas, argon gas, etc.). The drying gas temperature is preferably 40xcx9c150xc2x0 C. from the productivity point of view and in terms of the prevention of thermal degradation of the resin composition.
The drying time depends on the water content of the pellet and the treating load size but a drying time of about 15 minutesxcx9c72 hours is preferred from the productivity point of view and in terms of the prevention of thermal degradation of the resin composition.
While drying under the above conditions yields the objective boron compound (C)-containing EVOH (A) pellets, it is preferable to insure that the water-content of the pellets so dried will be 0.001xcx9c5 weight % (more preferably 0.01xcx9c2 weight %, particularly 0.1xcx9c1 weight part). If the water content is less than 0.001 weight %, the long-run moldability of the final resin composition of the invention will tend to be poor. On the other hand, if the water content exceeds 5 weight %, foaming tends to take place in the course of melt-kneading with polyamide resin (B) to be described below.
The boron compound (C)-containing EVOH (A) pellets thus obtained are then melt-kneaded with the polyamide resin (B). The method for this melt-kneading is not particularly restricted insofar as the boron compound (C)-containing EVOH (A) can be thoroughly melt-blended with the polyamide resin (B). Thus, any of the known pertinent techniques can be utilized. For example, the known kneading equipment such as Kneader-Ruder, an extruder, a mixing roll, a Banbury mixer, a plastmill, or the like can be employed. Usually, it is advisable to carry out the melt-kneading at 150xcx9c300xc2x0 C. (especially 180xcx9c280xc2x0 C.) for about 1 minute 1 hour. Industrially, an extruder such as a single-screw extruder or a twin-screw extruder is used with advantage and, where necessary, the extruder is preferably quipped with a vent suction means, a gear pump, a screen and/or other devices.
A high-quality resin composition with reduced thermal discoloration or degradation can be obtained by providing the extruder with one or more vent holes for application of suction forces to remove moisture and byproducts (low molecular products of thermal degradation etc.) and/or feeding an inert gas such as nitrogen gas continuously into a hopper to prevent infiltration of oxygen into the extruder.
The melt-kneading of the boron compound (C)-containing EVOH (A) with the polyamide resin (B) can be carried out by the following alternative methods, among others.
1) The method in which the boron compound (C)-containing EVOH (A) in solid form and the polyamide resin (B) are blended all at once and melt-kneaded.
2) The method in which the polyamide resin (B) in solid form is added to a molten mass of the boron compound (C)-containing EVOH (A) and the mixture is melt-kneaded.
3) The method in which the boron compound (C)-containing EVOH (A) in solid form is added to a molten mass of the polyamide resin (B) and the mixture is melt-kneaded.
4) The method in which the boron compound (C)-containing EVOH (A) and the polyamide resin (B), both in molten state, are blended and melt-kneaded.
 less than Other Additives greater than 
While the resin composition comprising said components (A), (B) and (C) according to the invention can be prepared by the above procedure, it is a recommendable procedure, for improving the thermal stability of the resin composition, long-run moldability, adhesion to the adhesive resin layer of a laminate, and heat-drawability to supplement the composition with an acid, such as acetic acid, phosphoric acid or the like, and/or a salt of the acid with a metal such as an alkali metal, alkaline earth metal, transition metal or the like. Incorporation of an alkali metal or alkaline earth metal salt is particularly effective.
The metal salt mentioned above includes salts of organic acids (acetic acid, propionic acid, butyric acid, lauric acid, stearic acid, oleic acid, behenic acid, etc.) with said metals and salts of inorganic acids (phosphoric acid, sulfuric acid, sulfurous acid, carbonic acid, etc.) with said metals (e.g. sodium salt, potassium salt, calcium salt, magnesium salt, etc.). Among these, acetates, phosphates and hydrogen phosphates are particularly suitable.
While the metal salt is formulated as needed in the resin composition described above, the concentration of the metal salt is preferably 5xcx9c1000 ppm (more preferably 10xcx9c500 ppm, particularly 20xcx9c300 ppm) as the metal relative to the resin composition. If the level of addition of the metal salt is less than 5 ppm, the effect of addition will not be sufficiently expressed. On the other hand, if the level exceeds 1000 ppm, the appearance of the shaped article will be unacceptably affected. When the resin composition contains two or more kinds of alkali metal and/or alkaline earth metal salts, the total of such salts is preferably within the above-mentioned range.
The technology of incorporating an acid or a metal salt thereof in the resin composition includes the method which comprises incorporating the acid or metal salt in EVOH (A) (when 2 or more EVOH species are used, at least one of them) in advance, the method which comprises incorporating the acid or metal salt in a composition prepared by blending EVOH (A) with polyamide resin (B), and the method representing a combination of the above two methods. In order to obtain a more prominent expression of the effect of the invention, the method comprising incorporating the acid or metal salt in EVOH in advance is preferred in view of the better dispersibility of the acid or metal salt.
The method which comprises incorporating the acid or metal salt in EVOH (A) in advance includes:
(a) the technique which comprises contacting a porous precipitate of EVOH having a water content of 20xcx9c80 weight % with an aqueous solution of the acid or metal salt and drying the resulting acid- or metal salt-incorporated EVOH;
(b) the technique which comprises adding the acid or metal salt in a homogeneous solution of EVOH (in water or alcohol), extruding the mixture in a strand form in a coagulation bath, cutting the strand into pellets and drying the pellets;
(c) the technique which comprises blending EVOH with the acid or metal salt and melt-kneading the resulting batch by means of an extruder or the like;
(d) the technique which comprises, in the course of preparation of EVOH, neutralizing the alkali (sodium hydroxide, potassium hydroxide or the like), used in the saponification step, with acetic acid or the like and washing the EVOH with water to adjust the amounts of residual acetic or other acid and byproduct alkali metal salt, such as sodium acetate, potassium acetate or the like, among other techniques.
For a more prominent expression of the effect of the invention, the above technique (a), (b) or (d) is preferred in view of the better dispersibility of the acid or metal salt thereof.
Furthermore, within limits not contrary to the object of the invention, the resin composition of the invention may be supplemented with the following ingredients:
lubricants such as saturated aliphatic amides (e.g. stearamide), unsaturated fatty acid amides (e.g. oleamide), bis-fatty acid amides (ethylene-bis-stearamide), fatty acid metal salts (e.g. calcium stearate, magnesium stearate, zinc stearate), low-molecular polyolefins (e.g. polyethylene or polypropylene of low molecular weight, i.e. about 500xcx9c10000), etc.;
inorganic salts (e.g. hydrotalcite),
plasticizers (e.g. aliphatic polyhydric alcohols such as ethylene glycol, glycerol, hexanediol, etc.),
oxygen absorbers [e.g. inorganic oxygen absorbers such as reducing iron powder, either as it is or in admixture with a water-absorbing substance, an electrolyte and/or other additive, aluminum powder, potassium sulfite, photocatalyst titanium oxide, etc.; organic oxygen absorbers such as ascorbic acid, its fatty acid esters and metal salts, hydroquinone, gallic acid, polyphenols such as hydroxyl-containing phenol-aldehyde resin, etc., bis-salicylaldehydeimine cobalt, tetraethylenepentamine cobalt, cobalt-Schiff""s base complex, porphyrines, macrocyclic polyamine complex, polyethyleneimine-cobalt complex and other coordination products of nitrogen-containing compounds with transition metals, terpene compounds, reaction products of amino acids with hydroxyl-containing reducing substances, triphenylmethyl compounds, etc.; polymer series oxygen absorbers such as coordination products of nitrogen-containing resins with transition metals (e.g. MXD nylon-cobalt complex) blends of tertiary hydrogen-containing resins with transition metals (e.g. polypropylene-cobalt blend), blends of carbon-carbon unsaturated bond-containing resins with transition metals (e.g. polybutadiene-cobalt blend), photooxidation-degradable resins (e.g. polyketones), anthraquinone polymers (e.g. polyvinylanthraquinone), and such formulations supplemented with aphotoinitiator (e.g. benzophenone), a peroxide acceptor (e.g. a commercial antioxidant) and/or a deodorizer (e.g. activated carbon), among others].
In addition, there may also be formulated various heat stabilizers, light stabilizers, oxidation inhibitors, ultraviolet absorbers, colorants, antistatic agents, surfactants, antimicrobial agents, antiblocking agents (e.g. finely divided talc), slip agents (e.g. amorphous silica), fillers (silicon oxide, titanium dioxide, clay, talc, bentonite, water-swellable phyllosilicate, etc.) and other resins (e.g. polyolefins, polyesters, polyamide resins melting at temperatures over 160xc2x0 C.), among others.
 less than Laminate greater than 
The resin composition of the invention, thus obtained, is very satisfactory in gas barrier properties, low-temperature heat-drawability, long-run melt-moldability and appearance and can of course be used as a single-layer artifact for various applications. However, it is useful in the form of a laminate.
It is particularly advantageous to use it in the form of a laminate consisting of the particular resin composition layer (X) and, as disposed on at least one side thereof, a thermoplastic resin layer (Y), and such a laminate has good water resistance, mechanical characteristics, heat-sealability and other properties of practical utility. Since such a laminate comprises the resin composition of the invention, it displays very satisfactory functions in terms of gas barrier properties, low-temperature heat-drawability, long-run melt-moldability and appearance. Such laminates are now described in detail.
In manufacturing a laminate, a second material (particularly, a thermoplastic resin) is laminated to one side or both sides of the resin composition of the invention. The laminating technology which can be used includes but is not limited to a method which comprises melt-extruding a second material in superimposition on a film or sheet of the resin composition of the invention, a method which comprises melt-extruding the resin composition of the invention to a second material, a method which comprises co-extruding the resin composition of the invention and a second material, and a method which comprises dry-laminating a layer of the resin composition of the invention and a layer of the second material with the aid of a known adhesive comprising an organotitanium compound, an isocyanate compound, a polyester compound, a polyurethane compound, or the like. The melt-forming temperature for the above melt-extrusion method is frequently selected from the range of 150xcx9c300xc2x0 C.
As said second material, a thermoplastic resin is useful. The thermoplastic resin includes but is not limited to the following:
polyolefin resins in a broad sense of the term, such as linear low-density polyethylene, low-density polyethylene, ultra-low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ionomers, ethylene-propylene (block or random) copolymer, ethylene-acrylic acid copolymer, ethylene-acrylate ester copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylate ester copolymer, homo- or copolymers of olefins, e.g. polypropylene, propylene-a-olefin (xcex1-olefin of 4xcx9c20 carbon atoms) copolymers, polybutene, polypentene, polymethylpentene, etc., such homo- or copolymers of olfins graft-modified with an unsaturated carboxylic acid or an ester thereof,
polyester resins,
polyamide resins (inclusive of co-polyamies),
polyvinyl chloride,
polyvinylidene chloride,
acrylic resins,
polystyrene resins,
vinyl ester resins,
polyester elastomers,
polyurethane elastomers,
chlorinated polyethylene
chlorinated polypropylene,
aromatic or aliphatic polyketones and
polyalcohols available on reduction thereof, and
other EVOH species.
The preferred, among these, from the standpoint of characteristics (particularly strength and appearance) or practical utility are polystyrene, polyolefins (e.g. polypropylene, ethylene-propylene (block or random) copolymer, polyethylene, ethylene-vinyl acetate copolymer), polyamides, polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). Particularly preferred is polystyrene which has good rigidity, transparency and surface gloss. Polyolefins which are advantageous from environmental points of view are also desirable.
When a second material is extrusion-coated on a film, sheet or other shaped article made of the resin composition of the invention or a film or sheet of the second material is laminated to the latter with the aid of an adhesive, said second material may be any of said thermoplastic resins and other desired materials (e.g. paper, metal foil, a uni- or biaxially oriented plastic film or sheet either as it is or with an inorganic substance vapor-deposited thereon, woven cloth, nonwoven cloth, metal flocs, wood, etc.).
The laminar structure of the laminate of the invention, when the layer of the resin composition of the invention is designated as X (x, x1, x2, . . . ), the layer of the second material, such as a thermoplastic resin layer, is designated as Y (y, y1, y2, . . . ), and the structure is a film, sheet or bottle, for instance, includes not only a binary structure consisting of x/y but also any suitable multi-layer structure such as
y/x/y,
x/y/x, x1/x2/y,
x/y1/y2,
y2/y1/x/y1/y2,
y2/y1/x/y1/x/y1/y2, among others.
Furthermore, when a regrind layer (a layer formed by crushing a laminate for reuse) comprising a mixture of at least said resin composition and thermoplastic resin is designated as R, the structure may for example be
y/R/x,
y/R/x/y,
y/R/x/R/y,
y/x/R/x/y,
y/R/x/R/x/R/y.
In the case of a filament, the mode of combination of x and y may be any of bimetal, core(x)-sheath(y), core (y)-sheath (x), offset (eccentric) core-sheath, and other types.
In the above laminar construction, an interlayer adhesive resin layer (AD) may be optionally interposed. As the adhesive resin, a variety of resins can be used. Interposition of the adhesive resin layer (AD) is preferred for obtaining a laminate with good drawability.
The preferred adhesive resin is dependent on the kind of y-layer resin and cannot be stated in general terms but a carboxyl-containing modified olefinic polymer obtainable by coupling an unsaturated carboxylic acid or acid anhydride to an olefinic polymer (said polyolefin resin in a broad sense of the term) chemically by addition reaction or graft reaction can be mentioned as a typical example. Specifically, it can be a polymer selected from among maleic anhydride graft-modified polyethylene, maleic anhydride graft-modified polypropylene, maleic anhydride graft-modified ethylene-propylene (block or random) copolymer, maleic anhydride graft-modified ethylene-ethyl acrylate copolymer, maleic anhydride graft-modified ethylene-vinyl acetate copolymer and the like. These may be used independently or two or more of them may be used in combination.
The amount of said unsaturated carboxylic acid or acid anhydride in the thermoplastic resin is preferably 0.001xcx9c3 weight %, more preferably 0.01xcx9c1 weight %, particularly 0.03xcx9c0.5 weight %. When the degree of modification of said modified polymer is too small, adhesion tends to be insufficient. On the other hand, when the degree of modification is too high, a crosslinking reaction may be induced to adversely affect moldability.
Furthermore, these adhesive resins may be blended with the resin composition of the invention, other EVOH species, rubber/elastomer components such as polyisobutylene, ethylene-propylene rubber, etc. and even the Y-layer resin. Particularly, blending a polyolefin resin different from the polyolefin-resin constituting the basis of the adhesive resin may result in improved adhesion.
The thickness of each layer as a component of the laminate is dependent on the overall laminar structure, kind of Y, end use or bottle shape, required physical properties, etc. and cannot be stated in general terms but is usually selected from the range of about 5xcx9c500 xcexcm (especially 10xcx9c200 xcexcm) for the X-layer, about 10xcx9c5000 xcexcm (especially 30xcx9c1000 xcexcm) for the Y-layer, and about 5xcx9c400 xcexcm (especially 10xcx9c150 xcexcm) for the adhesive AD layer. If the X-layer is less than 5 xcexcm thick, not only will the gas barrier properties be inadequate but thickness control will become unsteady. On the other hand, if the thickness exceeds 500 xcexcm, the impact resistance will become insufficient and an economic disadvantage will result. If the Y-layer is less than 10 xcexcm thick, the rigidity will be insufficient. On the other hand, if the thickness of the Y-layer exceeds 5000 xcexcm, the weight will be increased and the cost burden will be great. If the thickness of the adhesive resin (AD) layer is less than 5 xcexcm, not only will the interlayer adhesion be insufficient but thickness control will become unsteady. On the other hand, if the thickness of the (AD) layer exceeds 400 xcexcm, the weight will become excessive and an economic disadvantage will be inevitable.
The particularly preferred laminar structure for vessels includes
1. xe2x80x9cpolystyrene resin layer (Y1)/adhesive resin layer (AD)/resin composition layer (X)/adhesive resin layer (AD)/polystyrene resin layer (Y1)xe2x80x9d
2. xe2x80x9cpolyolefin resin layer (Y2)/adhesive resin layer (AD)/resin composition layer (X)/adhesive resin layer (AD)/polystyrene resin layer (Y1)xe2x80x9d
3. xe2x80x9cpolyolefin resin layer (Y2)/adhesive resin layer (AD)/resin composition layer (X)/adhesive resin layer (AD)/polyolefin resin layer (Y2)
In the above structure 1, a polystyrene resin layer (Y1) with good rigidity, transparency and surface gloss is disposed as two outermost layers constituting the inside and outside walls of a vessel.
In the above structure 2, preferably a polyolefin resin layer (Y2) (particularly a polyethylene resin layer) with good heat-sealability is disposed as the outermost layer constituting the inside surface of a vessel and a polystyrene resin layer (Y1) with good rigidity, transparency and surface gloss is disposed as the outermost layer constituting the outside surface of the vessel.
In the above structure 3, a polyolefin resin layer (Y2) (particularly a polyethylene resin layer) is disposed as the outermost layer constituting the inside wall of a vessel and a polyolefin resin layer (Y1) (particularly a polypropylene resin layer or a polyethylene resin layer) is disposed as the outermost layer constituting the outside wall of the vessel. This structure (3) is useful for applications where the use of polystyrene resin is restricted for environmental reasons.
 less than Heat-drawing greater than 
The above laminate can be used as such in various forms but since the resin composition of the invention has good gas barrier properties, low-temperature heat-drawability, long-run melt-moldability and appearance as mentioned above, it is also a good practice to subject it to thermal stretching for the purpose of improving its physical properties or forming it into vessels having desired shapes with greater success.
The term xe2x80x9cheat-drawingxe2x80x9d as used herein means an operation in which a uniformly heated laminate in the form of a film, sheet or parison is uniformly molded into a cup, tray, tube, bottle, film or the like by chuck, plug, vacuum, compressed air, blow, or other means. The drawing may be whichever of uniaxial and biaxial stretching, and it is advisable to carry out the stretching at as high a draw ratio as possible, for a drawn article with good gas barrier properties can then be obtained without troubles such as the incidence of pinholes and cracks during stretching, uneven stretching, irregular section, or delamination.
The stretching technology which can be used includes various methods providing for high draw ratios as selected from among roller stretching, tentering, tubular extrusion stretching, stretch blowing, vacuum forming, air pressure forming, and vacuum/air pressure forming. In the case of biaxial stretching, whichever of the concurrent biaxial stretching technique and the sequential biaxial stretching technique can be used. For the production of vessels such as cups and trays, draw-molding techniques such as vacuum forming, air pressure forming, vacuum-air pressure forming and plug-assisted vacuum-air pressure forming are important. In such processes, a uniformly heated multi-layer sheet is drawn into vessels, such as cups and trays, by chuck, plug, vacuum, air-pressure or other means.
The drawing temperature is selected from the range of about 60xcx9c170xc2x0 C., preferably about 80xcx9c160xc2x0 C., more preferably about 100xcx9c140xc2x0 C. The lower the drawing temperature is, the higher is productivity and, therefore, it is preferable to select as low a temperature as possible for heat-drawing.
After drawing, it is good practice to carry out heat setting. The heat setting can be made by the well-known technology. Thus, with the stretched film held under tension, it is heat-set at 80xcx9c170xc2x0 C., preferably 100xcx9c160xc2x0 C., for about 2xcx9c600 seconds.
When the laminate is to be used for shrink-packaging of raw meat, processed meat, cheese or the like, the stretched film is not heat-set but used as it is. Thus, said raw meat, processed meat, cheese or the like is accommodated in said film and heated at 50xcx9c130xc2x0 C., preferably 70xcx9c120xc2x0 C., for about 2xcx9c300 seconds to cause the film to shrink into intimate contact with the food.
The shape of the laminate is not particularly restricted but includes film, sheet, tape, cup, tray, tubing, bottle, piping, filament and profile shapes, to mention just a few examples. Where necessary, the laminate may be subjected to heat treatment, cooling, rolling, printing, dry lamination, solution or melt coating, bag-making, deep drawing, box-making, tube formation, splitting and other treatments.
When the heat-drawing is draw molding, among them, the draw ratio for a multi-lamellar vessel is preferably in the range of 4xcx9c20. With a draw ratio of less than 4, only shallow vessels can be fabricated which cannot be substituted for metal cans for beverages, thus being limited in applicability. On the other hand, with a draw ratio in excess of 20, a local variation in section and breaks tend to take place on the lateral part of the multi-lammelar vessel, thus detracting from the marketability of the product. The preferred range of draw ratio is 4xcx9c15, the more preferred range is 5xcx9c10, and the most preferred range is 6xcx9c10.
The term xe2x80x9cdraw ratioxe2x80x9d is used herein to mean the ratio of S1/S0 where S0 is the area of a sheet to be heat-stretched and S1 is the area of the sheet which has been heat-stretched. Taking a cup-shaped vessel as an example, the surface area of the cup top corresponds to S0 and the sum of the surface area of the lateral side and that of the cup bottom corresponds to S1.
The above vessel, e.g. cup, tray, tube or bottle, and the bag, cover or the like made of the drawn film, obtained as described above, are of use as containers for general foods, condiments, fermented foods, oleaginous foods, beverages, cosmetic products, pharmaceutical products, detergents, perfumes, fragrances and other aromatic products, industrial chemicals, agrochemicals, fuels and other products.
Particularly when the heat-drawn multi-lamellar vessel of the invention is a cup-shaped one, it is of use as a container for semisolid foods or condiments, e.g. jellies, puddings, yogurt, mayonnaise, miso, etc. and liquid beverages or condiments, e.g. salad oil, mirin, refined sake, beer, wine, juices, black tea, sport drinks, mineral water, milk, yogurt drinks and so forth.
When the heat-drawn multi-lamellar vessel of the invention is a tray-shaped one, it can be used with advantage as a tray for raw meat or processed animal meat products (ham, bacon, Vienna sausages, etc.).